This invention relates to the purification of tertiary butyl alcohol by contacting the impure tertiary butyl alcohol with at least two solid adsorbents comprising aluminum oxide and a large pore zeolite such as zeolite X. The process is especially useful for the separation of minor amounts of close boiling oxygenated impurities from the tertiary butyl alcohol.
Generally tertiary butyl alcohol as produced by oxidation processes such as the Oxirane Process contains small but significant amounts of impurities is including water, isopropanol, acetone, methyl ethyl ketone, isobutanol, formate esters, secondary butyl alcohol and the like. In certain applications, the presence of such impurities causes problems with respect to the desired use. For example, xe2x80x9chigh purityxe2x80x9d tertiary butyl alcohol is needed as a reagent for the synthesis of specialty products such as pharmaceuticals and agrichemicals, as a stabilizer of chlorinated hydrocarbons, in addition to other applications. It is thus desirable to provide a process by which the impurities can be conveniently separated from impure tertiary butyl alcohol to produce xe2x80x9chigh purityxe2x80x9d tertiary butyl alcohol.
It is known that the close boiling oxygenated impurities can be separated to a significant degree from tertiary butyl alcohol by an elaborate and extensive distillation procedure. For example, see U.S. Pat. No. 4,239,926. However, such procedures are costly and time-consuming, involving substantial capital investments and utilities expenses.
Further research has focused on developing less costly or time-consuming purification processes. For instance, U.S. Pat. No. 4,543,432 shows the separation of isopropanol from a tertiary butyl alcohol process stream by absorption using an asymmetric carbonaceous absorbent such as Ambersorb(copyright) XE-347. Data are presented in Table 11 giving the equilibrium capacity of isopropanol on various adsorbents for a synthetic solution of isopropanol in tertiary butanol. Data for Type 5A and 13X molecular sieves indicate that Type 5A has a slightly higher equilibrium capacity than Type 13X. Additional data relative to Type 5A are given in Table IV. In addition, U.S. Pat. No. 6,417,412 teaches the purification of a tertiary butyl alcohol process stream by contact with a large pore zeolite in the sodium form (such as 13X).
In sum, new processes for the purification of tertiary butyl alcohol are needed. It is desirable to develop a simplified procedure whereby tertiary butyl alcohol process streams can be conveniently treated to separate close boiling impurities by a relatively simple and straightforward procedure.
The invention is a method of purifying tertiary butyl alcohol containing minor amounts of impurities. The method comprises contacting the tertiary butyl alcohol with at least two solid adsorbents comprising aluminum oxide and a large pore zeolite such as zeolite X or Zeolite Y. As a result of this contact, impurities are retained on the zeolite and alumina and are thus removed or separated from the tertiary butyl alcohol; product tertiary butyl alcohol reduced in the content of contaminating impurities is readily recovered. It is generally advantageous to operate with a plurality of contact zones since the contact material must be regenerated from time to time as it loses its effectiveness for impurities removal over extended use. With a plurality of treatment zones, tertiary butyl alcohol can be treated in one zone while a separate zone is being regenerated.